1. Field of the Invention
The present invention relates to a positioning apparatus, an exposure apparatus, and a method of manufacturing a device.
2. Description of the Related Art
In general, an exposure apparatus includes a driving unit including a movable element and stator, a laser interferometer for measuring the position of a stage which moves by the driving unit, a supply unit which supplies a temperature-regulated gas to the light path of measurement light from the laser interferometer, and a recovery unit which recovers the gas. An exposure apparatus required to achieve a positioning accuracy on the level of several nanometers must control the environmental conditions in the exposure apparatus, such as the temperature, humidity, and pressure, constant. Hence, a change in environment is suppressed by supplying a gas having, for example, an accurately controlled temperature from the gas supply unit into the entire apparatus in one direction.
The exposure apparatus often uses a linear motor which can be driven in a non-contact manner as a driving device for a substrate stage which holds a substrate. The linear motor generally uses coils which generate a very large amount of heat upon energization and are therefore one of main heat sources in the exposure apparatus. Hence, the amount of heat generated by the linear motor must be kept small when the exposure apparatus is used in an environment having a temperature controlled constant. For this reason, a technique of containing coils in a jacket, and supplying a coolant to the coils, thereby recovering heat generated by the coils is widely employed. However, it is difficult to sufficiently recover the heat generated by the coils and maintain the surface temperature of the linear motor uniform. Japanese Patent Laid-Open No. 2006-216866 discloses a technique of surrounding a driving unit using a chassis so as to separate it from a stage space, and evacuating the chassis through exhaust ducts, thereby preventing an atmosphere heated by heat which cannot be removed by a coolant from leaking to the stage space.
In the related art technique disclosed in Japanese Patent Laid-Open No. 2006-216866, a movable element and a stage are connected to each other via a connecting member, and an opening is formed in the chassis along the moving range of the connecting member. Hence, as the connecting member moves in the opening at high speed, the gas around the opening is disturbed, is heated by heat generated by the driving unit, and then leaks to the stage space. Further, as the movable element moves to the end of the chassis at high speed, the gas between the chassis and the movable element is compressed, heated, and then pushed out from the end of the opening. In the exposure apparatus, the speed and acceleration of the stage are increasing in order to improve the throughput, so a heated gas is more likely to leak to the stage space.
To prevent the leakage of a heated gas to the stage space, it is possible to increase the amount of exhaust from the chassis which surrounds the driving unit. However, as the amount of exhaust increases, the flow of the gas supplied by the supply unit to condition the air in the stage space is disturbed more, so the air in the light path of the interferometer may fluctuate. Furthermore, due to the increase in amount of exhaust, the size of the air-conditioning equipment of the exposure apparatus may increase, leading to a rise in apparatus cost. In this manner, unless it is possible to sufficiently ensure the reliability of exhaust from the driving unit corresponding to a speedup of the stage, a heated gas leaks from the chassis which surrounds the driving unit to the stage space. That heated gas flows to the vicinity of the stage along the flow of the gas supplied from the gas supply unit. Furthermore, upon driving of the stage, the stagnant gas rolls up and spreads to the entire apparatus, thus influencing the laser interferometer.